The present invention relates to three-dimensional structural products, and more particularly to structural products made from wood products and methods of forming same.
Structural panels can be used in a variety of applications, including applications similar to those in which plywood or lumber conventionally are used. For instance, structural panels can be used in the construction of pallets. Pallets and similar support devices are common articles that are used to transport goods in a variety of industries. Pallets can come in many shapes and sizes, and are typically formed from wood planks or molded plastic. While these types of pallets are commonplace, they suffer from several disadvantages. First, pallets formed from wood planks require first quality pieces that are free from serious defects that could compromise the integrity of the pallet. Not only does obtaining quality wood add to the cost of the pallet, a significant portion of the supply trees are wasted during production. In addition, the wood planks forming the pallet are typically nailed together. The nailed joints may be sturdy at first, but they tend to fail due to the rigors of transporting goods. In fact, normal use typically destroys most pallets after an alarmingly low number of uses, as weather, product weight, and mishandling all play a role in their demise. Instead of repairing broken pallets, however, most users simply throw the pallets away, which creates further waste and increases the costs of transporting goods.
Molded plastic panels are also disadvantageous, in that they are constructed of non-natural materials that do not break down after the panels have been discarded. Plastic panels also tend to have low bending resistance, which limits the applications suitable for plastic panels.
Structural panels have been developed that address some of the shortcomings of wood plank and plastic panels. For example, U.S. Pat. No. 4,702,870 to Setterholm et al., the disclosure of which is incorporated herein by reference, discloses molded panels made of wood fiber from hardwood trees that are relatively small, deformed or otherwise not well shaped to produce commercial sizes and quantities of lumber, and limbs of larger hardwood trees that are not utilizable for lumber. Setterholm's panels utilize wood fibers that are processed into a slurry and then deposited on top of a mold. A normal force is applied to the slurry in conjunction with heat and vacuum to form the panel structure. One advantage of the Setterholm panels is that many different types of wood fibers, including soft wood fibers and hardwood fibers, can be used in the invention to more efficiently utilize the wood resources currently available.
Unfortunately, the inventors of the present invention have discovered that panels created by the teachings of Setterholm and/or similar techniques are susceptible to significant deformation when placed under load. This deformation can lead to immediate failure of the panel or greatly reduce the fatigue lifespan of the panel. Because of the nature of the materials forming the panel, there is a need to improve the bending resistance of such panels. There is also a need for forming a panel that has improved structural properties, yet that remains low in cost and can be produced efficiently.